1. Field of the Invention
The present invention relates to a coated film manufacturing method and a coating machine.
2. Description of the Related Art
In manufacturing a coated film such as an optical film, a coating liquid is supplied to a continuously-traveling web by a die coater. In recent years, a technique of forming a precise coat with a thinner wet thickness is required to exhibit a desired function.
In order to form a precise coat with a thinner thickness, it is necessary to reduce the clearance between a die coater and a web and to maintain the clearance with high accuracy. However, even when the clearance between the die coater and the web is positioned with high accuracy, the die coater may be deformed due to a variation in temperature of the die coater. Accordingly, there is a problem in that the accuracy of the set clearance cannot be maintained.
To solve this problem, JP1993-004066A (JP-H05-004066A) discloses a coating machine in which heat-retention water is circulated in a die coater and the entire die coater is coated with a heat-insulating material.
When a coating liquid adheres to the die coater and an organic solvent in the coating liquid is evaporated, heat is released from the die coater. Accordingly, the temperature of the die coater varies and thus the die coater is deformed. Particularly, in a standby state before coating, the coating liquid is made to flow from the die coater until the supply of the coating liquid is stabilized. Accordingly, the evaporation is large and the deformation due to the variation in temperature of the die coater is particular noted.
To solve this problem, JP2005-270878A discloses a technique of preventing a coating liquid from coming in contact with a die coater by attaching a heat-insulating plate to a part of the outer circumference of the die coater or coating the part of the outer circumference of the die coater with a heat-insulating material.